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Thermistor

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Boncuk

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Hi to all,

I am not familiar with the term thermistor. I know it is some device to measure temperature though, but I have no idea if a thermistor has a positive or a negative temperature coefficient. German terms say clearly NTC (negative going) or PTC (positive going) resistance value with increasing temperature.

If a thermistor has a posivite temperature coefficient it can be replaced by any bad qualitiy carbon layer resistor which changes value considerably with increasing temperature. :)

So what coefficient does a thermistor normally have? :confused:

Regards

Boncuk
 
THere are many thermistors and they each have their own temperature-resistance curve. You could replace the thermistor by whatever you want as long as the resistance of the new component is within the range of the old circuit and you recalibrate for the different curve.

I think PTCs have a very sharp change in resistance with temperature though and as such are used more for current limiting rather than temperature measurement. NTCs are normally used for temeprature measurement from what I have seen because the change is more gradual.

THe thermistor will still change resistance far FAR more than a bad carbon resistor will over temperature though (even more than RTDs, the other resistive temperature sensor,...though that's not saying much). Like you would need a seriously bad, unstable, yet predictable resistor. I don't even know if they exist. You could try it though.
 
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I just looked at wikipedia, and their description looks like a lot of math, but thermistors come in a wide variety.

Pick a thermistor and look at its data sheet.
 
Hi friends,

talking about a thermistor is about the same as talking about any vehicle. A vehicle could be a truck, a sedan or anything else, even a ship. A thermistor could also be anything, PTC or NTC.

That's absolutely no precise describtion. Not your fault though. :D

Regards

Boncuk
 
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